Process for adsorbent bleaching of edible oils

ABSTRACT

In a process for adsorbent bleaching of edible oils, adsorbent agent usage is reduced by deaerating and moisture adjusting an oil/adsorbent mixture, then adjusting the temperature of the mixture to range from 200* to 400* F and then directly passing the temperature-adjusted mixture through a bleaching zone at a pressure of atmospheric pressure or greater in the substantial absence of oxygen and under turbulent flow, and finally filtering the adsorbent from the oil. Adsorbent usage is also reduced by utilizing the above deaerating, moisture adjusting, and temperature conditions with or without the use of turbulent flow and utilizing 2 to 7 bleaching stages with more or less equal amounts of fresh adsorbent being used in each stage. Preferably, this multistage process is utilized in combination with the turbulent flow process.

Elnited States Patent Harris et al.

amuse June 27, 1972 [54] PROCESS FOR ADSORBENT BLEACHING 0F EDIBLE OILS [72] Inventors: Ronald D. Harris, Wyoming; Leon Levine,

' Cincinnati, both of Ohio [73] Assignee: The Procter & Gamble Company, Cincinnati, Ohio [22] Filed: Sept. 4, 1969 [21] Appl. No.: 855,352

[52] U.S. Cl ..260/428 [51] Int. Cl. ..Cl1b3/l0 [58] Field of Search ..260/428, 427

[56] References Cited UNITED STATES PATENTS 3,590,059 6/1971 Velan ..260/423 2,428,082 9/1947 King et a1 .....260/428 2,569,124 9/1951 Christenson et al. .....260/428 2,639,289 5/1953 Vogel ..260/428 2,781,301 2/1957 Payne ..196/l47 Assistant Examiner-Ethel G. Love Attorney-Edmund J. Sease [57] ABSTRACT In a process for adsorbent bleaching of edible oils, adsorbent agent usage is reduced by deaerating and moisture adjusting an oil/adsorbent mixture, then adjusting the temperature of the mixture to range from 200 to 400 F and then directly passing the temperature-adjusted mixture through a bleaching zone at a pressure of atmospheric pressure or greater in the substantial absence of oxygen and under turbulent flow, and finally filtering the adsorbent from the oil. Adsorbent usage is also reduced by utilizing the above deaerating, moisture adjusting, and temperature conditions with or without the use of turbulent flow and utilizing 2 to 7 bleaching stages with more or less equal amounts of fresh adsorbent being used in each stage. Preferably, this multistage process is utilized in combination with the turbulent flow process.

22 Claims, No Drawings PROCESS FOR ADSORBENT BLEACHING OF EDIBLE OILS BACKGROUND OF THE INVENTION The field of this invention is the processing of edible fats and oils.

In the processing of edible fats and oils, triglyceride oil having been extracted from an oil-bearing material of animal, vegetable or marine origin is refined, bleached, and deodorized. A water washing step can be interspersed between the refining and the bleaching step. Hydrogenation and blending or winterization steps can be interspersed between the bleaching and deodorizing steps. The present invention relates especially to the bleaching step and particularly to the adsorbent bleaching of refined edible oils.

The type of bleaching step which is utilized depends on the type of oil to be bleached. Palm oil and coconut oil which ordinarily contain predominantly carotenoid color bodies (these are characterized by a red color) are ordinarily bleached by a heat bleaching process. In this heat bleaching process the oil to be bleached is ordinarily heated to a temperature ranging from 400 to 480 F and maintained at this temperature for from about minutes to about 4 hours. As a result of this processing, the red color bodies enter into a chemical reaction whereby their characteristic red color is lost, and the oil subjected to this process takes on a very light-colored appearance. Oils containing predominantly carotenoid color bodies can also be bleached utilizing an adsorbent bleaching process. This type of process is described in more detail below.

Some oils previous to bleaching, such as soybean, cottonseed and sunflower seed oils contain not only carotenoid color bodies but also color bodies derived from chlorophyll and closely related compounds. These chlorophyll-type compounds impart a green color to the oil. If these oils are subjected to heat bleaching, the carotenoid color bodies are converted so as to possess a wry light-colored appearance but the chlorophyll-type color bodies are not. Although the green color of the chlorophyll bodies is not apparent when carote noid pigments are also present, it becomes apparent if the carotenoid color bodies are bleached out by heat bleaching which does not affect the chlorophyll-type color bodies. If oil containing chlorophyll-type color bodies is then subjected to a hydrogenation process, the product can become a brilliant green. Thus, heat bleaching is unsuitable for oils containing chlorophyll-type color bodies especially if these oils are to be hydrogenated. These chlorophyll-type color bodies as well as the carotenoid color bodies which are present can be bleached from these oils by the use of an adsorbent bleaching process.

In a typical adsorbent bleaching process, refined triglyceride oil is admixed with adsorbent. This mix is heated up, maintained in heated condition for a period of time, and then filtered to separate the spent adsorbent and decolorized oil. Traditionally, much of the bleaching action occurs during the filtering process because of the high concentration of bleaching adsorbent compared to oil which can be present in this process. This bleaching effect during filtering is referred to as a press bleaching effect. This adsorbent bleaching process works because the color-forming bodies are adsorbed in the adsorbent. The heating enhances the bleaching effect of the adsorbent, for example, by inducing a more favorable equilibrium between adsorbent and oil color bodies (that is, by increasing the amount of color bodies the adsorbent is capable of adsorbing), and by increasing the adsorption rate. Once the color bodies are adsorbed, they are removed and decolorized oil is produced as a result of the filtering step.

The amount of adsorbent utilized depends in part upon the initial color of the oil to be processed and on the final color desired. The initial color of a refined oil depends on the effectiveness of the refining process utilized and on the type of oil which is present. The color of oil is ordinarily characterized by comparison-of the oil to Lovibond Red standards mentioned on pages 132 and 133 of Baileys Industrial Oil and Fat Products, 3rd Edition (1964), John Wiley & Sons, New York. The color is further characterized by the parts per million (hereinafter ppm) of chlorophyll which is present. The Lovibond Red color measurement denotes the amount of carotenoid color bodies which are present; the chlorophyll measurement denotes the chlorophyll-type color bodies, that is, the green color bodies which are present. Refined soybean oil previous to bleaching typically has a Lovibond Red value ranging from 9 to 15 and a chlorophyll weight content ranging from 0.2 to 1.0 ppm; it is usually desirable to bleach this refined oil so that it has a Lovibond Red value of less than 8, preferably less than 6, and a chlorophyll content of less than 0.1 ppm by weight, preferably less than 0.03 ppm by weight. Refined cottonseed oil previous to bleaching typically has a Lovibond Red color value ranging from 3 to 15 and a chlorophyll weight content ranging from 0.2 to 1.0 ppm; in a bleaching operation it is usually desirable to achieve a Lovibond Red value for the oil of less than 8, preferably less than 6, and a chlorophyll content of less than 0.1 ppm, preferably less than 0.33 ppm. A refined sunflower seed oil previous to bleaching ordinarily has a Lovibond Red value ranging from 2 to 4 and a chlorophyll weight content ranging from 0.1 to 0.4 ppm; although the Lovibond value previous to bleaching is a satisfactory final color, the initial chlorophyll content is not satisfactory and therefore it is usually desirable to bleach refined sunflower seed oil to possess a chlorophyll content less than 0.1 ppm by weight, preferably less than 0.03 ppm by weight. A refined palm oil previous to bleaching typically has a Lovibond Red color value ranging from 50 to 250 and has essentially no chlorophyll content; it is usually desirable to bleach refined palm oil to possess a Lovibond Red color value ranging from 20 to 30. A refined coconut oil previous to bleaching typically has a Lovibond Red color value ranging from 2 to 4 and has essentially no chlorophyll content; it is usually desirable to bleach refined coconut oil to possess a Lovibond Red color value ranging from 0.7 to 1.5. According to the previously mentioned Baileys Industrial Oil and Fat Products at page 773, processors of edible cottonseed and soybean oil'products ordinarily use about 1.0 percent of high grade adsorbent during the bleachingoperation.

A reduction in the amount of adsorbent utilized during bleaching is desirable on two counts first, the adsorbent itself costs money and a reduction in its usage reduces the expense of processing the oil. Secondly, the adsorbent adsorbs and traps within itself a weightof oil approximately equal to its own weight. Thus, the more adsorbent that is utilized during the bleaching operation, the more the oil is that has to be reclaimed from the spent adsorbent or is lost from the processing stream in spent adsorbent which is discarded. Thus, processes which reduce the amount of adsorbent utilized, that is, which increase adsorbent usage efficiency, are highly desirable.

Adsorbent bleaching operations are well known in the art. Typical processes are presented in Glenn, U.S. Pat. No. 2,292,027; King et al., U.S. Pat. No. 2,428,082; Robinson, U.S. Pat. No. 2,483,710; Bailey, U.S. Pat. No. 2,618,644; Mc- Michael et al., U.S. Pat. No. 2,717,256; British Pat. No. 846,474; and in Bailey's Industrial Oil and Fat Productspreviously mentioned at pages 769 through 792. None of these referenced discloses all of the conditions of any of the embodiments of the present invention; the disclosed methods are in large measure inferior to the methods of the present invention so far as adsorbent efficiency usage is concerned.

SUMMARY OF THE INVENTION It has been discovered that in a process for the bleaching of refined edible oils with adsorbent, adsorbent usage can be reduced at least 20 percent, with adsorbent usages of 0.5 percent by weight of the oil or less being typical for bleaching refined soybean oil, by the use of the first embodiment of this invention. In this embodiment, an oil/adsorbent mixture is formed, is deaerated, has its moisture level adjusted to be within special essential limits, has its temperature adjusted to range from 200 to 400 F and is then directly and continuously passed through a bleaching zone at a pressure of atmospheric pressure or greater in the substantial absence of oxygen under turbulent flow, and then filtered.

In a second embodiment of this invention, savings of at least 20 percent adsorbent are also achieved in a process for the bleaching of refined edible oils with adsorbent. In this embodiment the mixture-forming, deaeration, moisture adjusting, and temperature adjusting steps of the first embodiment are utilized, and the mixture once temperature adjusted is directly and continuously passed through a bleaching zone at a pressure of atmospheric pressure or greater in the substantial absence of oxygen and filtered, but the flow through the bleaching zone need not be turbulent. Despite the fact that the turbulent flow does not need to be utilized, high bleaching efficiencies are achieved because the bleaching operation of this embodiment is carried out in 2 to 7 stages, with fresh adsorbent being utilized in each stage.

In a preferred process for the bleaching of refined edible oils with adsorbent, the turbulent flow process, that is, embodiment 1 herein, is combined with a multistage process, embodiment 2 herein. In this preferred process, bleaching adsorbent usage is reduced at least 50 percent. For soybean oil bleaching, adsorbent usage of 0.25 percent or less based on the weight of the oil, is typically achieved.

DETAILED DESCRIPTION OF THE INVENTION Turning first of all to the first embodiment of this invention described broadly above, refined edible oil which has preferably been water-washed is admixed with bleaching adsorbent to form a mixture of said oil with said adsorbent. The oil which is to be processed herein can have been subjected to no bleaching previously or can have been partially bleached previously by any convenient process.

The adsorbent for use herein can be any of those typically used for the bleaching of refined oils. For example, bleaching earths and acid-activated clay bleaching agents are suitable for use herein. A very useful adsorbent is Filtrol 105. Filtrol 105 is prepared by treating magnesium silicate with phosphoric acid; it has a pH of 2.3 and is a beige powdery material. Ordinarily these adsorbents are utilized in particulate form and contain more than 65 percent of their particles having an equivalent diameter ranging from 0.5 to microns; the rest of the particles ordinarily have a size between 15 microns and 25 microns. The adsorbent utilized herein can be fresh or partially spent.

As previously indicated, the amount of adsorbent to be utilized depends on the effectiveness of the refining process previously utilized and on the type of oil which is present. Typical amounts of adsorbent to be utilized herein are presented hereinafter.

The admixing of oil and bleaching adsorbent can be carried out by any conventional method, for example, in a conventional stainless steel mixing tank.

In a preferred method of admixing oil and adsorbent, a concentrate of oil and adsorbent is first formed, for example, in a tank equipped with an agitator. The concentrate contains all of the adsorbent and a very small proportion of the oil which is to be bleached, for example, 0.25 to 2 percent by weight of the oil which is to be bleached. This concentrate is then continuously admixed with the main stream of oil to be bleached, for example, by injecting the concentrate into the oil stream previous to a pump or by injecting the concentrate into the oil stream in a pipe previous to a mixing orifice.

Preferably the oil and adsorbent during admixing are maintained at temperatures less than 150 F so as to minimize oxidation of the oil since such oxidation results in darkening of the oil.

Preferably, the admixing times are minimized so as to minimize the chance for oxidation. Thus, in a batch operation times of about 5 minutes or less are recommended. In a continuous operation admixing occurs essentially instantaneously; it is thus preferred over a batch system.

If the oil/adsorbent mixture or the concentrate is formed in a batch process, the mixture or concentrate during and upon its formation is preferably blanketed with an inert gas such as nitrogen to minimize or prevent oxidation of the oil.

The oil/adsorbent mixture once formed can have its temperature raised slightly, for example, up to 190 F, for example, by passage through a heat exchanger to improve the efficiency of the succeeding deaeration and moisture adjustment operations described hereinafter. This temperature increase is not essential for the invention herein and is simply a matter of choice for convenience in processing.

The oil/adsorbent mixture is then deaerated and has its moisture adjusted. The moisture content of the mixture previ ous to its deaeration and moisture adjustment generally is from 0.4 to 1 percent by weight of the total oil/adsorbent mixture. The oxygen content of the mixture entering this deaeration/moisture adjustment step ordinarily ranges from 2-3 volume percent of the total mixture. In this deaeration operation essentially all of the oxygen in the mixture is removed. In the moisture adjustment operation, the moisture level in the mixture is adjusted to range from 0.05 to 0.25 percent, preferably 0.075 to 0.15 percent by weight of the total mixture. This deaeration and moisture adjustment is essential to achieve the benefits of reduced adsorbent usage that is characteristic of the present invention. If oxygen is present, or if the moisture limits are outside of those specified herein, the adsorbing operation will become inefficient. The deaeration and moisture adjustment can be carried out in conventional equipment and preferably are carried out together. For example, these two operations can be carried out'in a, vacuum dryer. This vacuum dryer can be a round vertical tank into which the oil/adsorbent mixture is tangentially introduced at the top, and through the top of which is drawn a vacuum; this vacuum is ordinarily greater than 25 inches of mercury in other words, the absolute pressure is less than 5 inches of mercury. The deaeration and moisture adjustment operation is usually carried out in 10 seconds to one minute.

The deaerated/moisture-adjusted mixture then has its temperature adjusted to range from 200-400 F, preferably 275350 F. This temperature adjustment can conveniently be carried out, for example, in a conventional shell and tube heat exchanger. At temperatures below 200 F bleaching occurs more slowly and the bleaching equilibrium is less favorable in that the adsorbent is not capable of adsorbing as many color bodies. At temperatures above 400 F hydrolysis can occur converting some of the oil present to free fatty acid and glycerine and decreasing the yield from the process. If a heat exchanger is utilized to increase the temperature to this 200-400 F range, 50 to percent of the bleaching that occurs, typically occurs in this heat exchanger.

The oil/adsorbent mixture having had its temperature ad justed is directly and continuously passed through a bleaching zone. This bleaching zone extends from the point the abovedescribed the temperature of the mixture is adjusted to within the above described range until bleaching equilibrium is closely approached or until a desired point on the way to bleaching equilibrium is reached; bleaching equilibrium is closely ap proached when the bleaching adsorbent is spent. The temperature range of 200-400 F is maintained throughout the bleaching zone. The mixture has a residence time in the bleaching zone ranging from 0.5 minute to 30 minutes, preferably 3 minutes to 12 minutes. Generally, residence times less than 0.5 minute do not provide sufficient bleaching. Bleaching equilibrium is always reached in residence times of 30 minutes or less. The bleaching zone where this residence time occurs can consist of the temperature adjusting device, for example, the heat exchanger previously mentioned, any piping and any bleaching reactor as defined hereinafter to provide residence time previous to filtration. Preferably, the oil is bleached to the desired end point in this bleaching zone.

For this first embodiment of the present invention it is essential that the oil/adsorbent mixture be directly and continuously passedthrough the bleaching zone at a pressure of atmospheric pressure or greater in the substantial absence of oxygen and under turbulent flow.

The use of atmospheric pressure or greater is necessary so that the moisture level which has been carefully adjusted does not change, that is, so that the oil is not dried. Preferably, a positive pressure, that is, a pressure greater than atmospheric, is utilized so as to assure the exclusion of oxygen from the system. In general, the use of pressures greater than 150 psig is limited by the type of equipment which is available for use herein.

The substantial absence of oxygen is required because oxygen can oxidize the oil resulting in darkening.

Turbulent flow is required to provide high efficiency contact between the adsorbent and the oil. In other words, it provides localized mixing to enhance mass transfer between the adsorbent and the oil, and it also provides uniform contact time, assuring uniform results. If turbulent flow is not maintained, some-adsorbent and oil leave the bleaching zone before equilibrium is obtained, that is, before the bleaching potential of the adsorbent is fully utilized, thus reducing the potential adsorbing capability of the adsorbent. Turbulent flow is well known in the art and is described at page 375 of Perry's Chemical Engineers Handbook, 3rd Edition.

Turbulent flow in the temperature adjusting device and piping thereafter is produced by the velocity of the mixture being processed and the geometry of the system. A bleaching reactor, that is, a device utilized to provide additional residence time, if such is necessary, should be one which is utilized with turbulent flow conditions. Such reactors include, for example, well-stirred columns with baffles, or a series of well-stirred tanks, for example, three or more tanks in series, especially a series of well-mixed batch reactors whose operations are cycled to approximate continuous operation.

The preferred bleaching reactor for use herein as the remaining part of the bleaching zone other than the temperature-adjusting device and any interconnecting pipe (there may also be piping and heat exchangers downstream of the reactor and previous to filtration which are part of the bleaching zone), is a vertically oriented flooded packed column. The oil/adsorbent mixture is introduced into the bottom of the column and emits from the top of the column The column is flooded so as to assure the most effective use of its volume. In general, such columns have diameters ranging from 1.5 inches to feet, heights ranging from 5 feet to feet, and heightto-diameter ratios usually ranging from 3:1 to 75 I. In general, the void space in the column ranges from 85-98 percent, by volume, of the column, while the rest of the space in the column is taken up by packing. For these packed columns flow providing a Reynolds number ranging from 1 to 100, preferably 5 to 100 gives the required turbulent flow of this invention. The Reynolds number for a packed column is defined as the effective particle diameter of the packing multiplied by the fluid velocity multiplied by the fluid density divided by the fluid viscosity. The effective particle diameter of the packing is the diameter of a sphere having the same surface area per unit volume as the packing.

Examples of suitable packing materials are Pall rings, Hyperfil packing, Stedman packing, Sulzer packing, and Raschig rings, all of which are described by K. E. Porter et al. in Chemistry and Engineering (Feb. 4, 1967), at pages 182-188.

Of these packings, the most highly preferred are Pall rings which are commercially available in five-eighths inch, 1 inch, 1.5 inch, and 2 inch sizes. This is because Pall rings entrap the least adsorbent and provide the least back pressure buildup. While the other packings can be employed, they on the other hand entrap some adsorbent, increasing back pressure, requiring increased pumping costs and eventually requiring cleanout or new packings; adsorbent accumulation is also undesirable because it can cause hydrolysis of the oil.

Pall rings are a commercially available packing material (U.S. Stoneware Company, Akron, Ohio); similar packing is sold under the name Flexiring (Koch Engineering Company, Inc., Whichita, Kansas). These rings are stamped, preferably from stainless steel, and formed into open-ended cylinders of approximately equal outer diameter and height. The sides of the cylinders comprise 10 holes per cylinder formed by punching material from the sides to create 10 tongues extending into the center of the cylinder. Each tongue corresponds to, and is attached at the side of, a hole in the side of the cylinder. Except for the holes and tongues, the packing is similar to Raschig rings. Characteristics of the rings are more fully described by J. S. Eckert et al. in Chemical Engineering Progress 54, No. 1, 70-75 (Jan., 1958); 57, No. 9, 54-58 (Sept., 1961); 59, No. 5, 76-82 (May, 1963); and 62, No. I, 59-67 (Jan, 1966).

The packing material is preferably made from stainless steel. Ceramic or other packings can also be used, however, if they are of sufficient stability that they do not fracture.

The oil/adsorbent mixture having been exposed to the bleaching zone is then filtered to separate the used or spent adsorbent from the bleached, that is, decolorized oil. This filtering can be carried out, for example, by conventional filtering process in a filter press. If an open filter press is utilized the oil/adsorbent mixture is ordinarily cooled below F previous to filtration so as to minimize oxidation and resulting darkening of the oil. This temperature adjustment can be carried out in a conventional heat exchanger. Since essentially complete bleaching can be achieved in the bleaching zone, minimum or no press bleaching effect is required.

Preferably the filtration is carried out in the absence of oxygen by the filtering method described in Going et al. U.S. Pat. No. 3,414,129. Previous to filtering in this method the temperature of the oil/adsorbent mixture is preferably adjusted to 280 F or below if the filter medium is cloth, since temperatures above this level can reduce filter fabric life. Higher temperatures can be utilized if a filter media such as Teflon is utilized.

The oil emitting from the filter is bleached to the final Lovibond Red color previously described, and to the final chlorophyll levels previously described, while the amount of adsorbent utilized is reduced significantly over amounts conventionally used. For example, soybean oil or cottonseed oil is bleached to a Lovibond Red color of less than 8, and a chlorophyll content of less than 0.1 ppm by the use of 0.15 to 0.5 percent by weight of the oil, normally 0.35 to 0.45 percent by weight of the oil, of an acid-activated bleaching clay adsorbent such as Filtrol 105. To bleach sunflower seed oil or coconut oil utilizing this process the amount of adsorbent required normally ranges from 0.1 to 0.3 percent by weight of the oil. To bleach palm oil utilizing this process, the amount of adsorbent normally ranges from 0.2 to 0.5 percent by weight of the oil. In all cases this is at least a 20 percent reduction over typical bleaching processes.

The above described first embodiment is also adaptable to and advantageous in a multistage countercurrent process of the type described at page 778 of Bailey's Industrial Oil and Fat Products, 3rd Edition (1964), John Wiley & Sons, New York. In this process partially used up adsorbent is utilized to partially bleach fresh (i.e., unbleached) oil. The partially bleached oil is then bleached to the desired end point in a final bleaching stage by the use of fresh adsorbent. The fresh adsorbent is only partially used up in this final bleaching stage; it is then used to partially bleach fresh oil. In this process in any or all stages the present process is desirably utilized. Thus, any or all stages of a countercurrent process can involve the admixing, deaerating, moisture adjusting, temperature adjusting, passing through a bleaching zone and filtering under the conditions required for the first embodiment of this invention.

In the second embodiment of this invention the mixtureforrning, deaeration, moisture adjusting and temperature adjusting steps of the first embodiment are utilized. Moreover, the mixture once temperature adjusted is directly and continuously passed through a bleaching zone at a pressure of atmospheric pressure or greater in the substantial absence of oxygen. Moreover, the adsorbent is filtered from the oil. However, in this embodiment the flow through a bleaching zone need not be turbulent; in other words, the flow through a bleaching zone can be turbulent or non-turbulent or a combination of both. Despite the fact that turbulent How does not need to be utilized, high bleaching efficiencies are achieved because the bleaching operation of this embodiment is carried out in 2 to 7 stages with fresh adsorbent being utilized in each stage. The amount of adsorbent utilized in each stage is preferably equal to 100/12 t 20% by weight of the total adsorbent wherein n is the number of stages.

Thus, the process of this second embodiment comprises a first stage which comprises admixing oil and fresh bleaching adsorbent to form a mixture; deaerating said mixture and adjusting its moisture content to range from 0.05 to 0.25 percent by weight of the mixture; adjusting the temperature of said mixture to range from 200 to 400 F; directly and continu ously passing this mixture through a bleaching zone at a pressure of atmospheric pressure or greater in the substantial absence of oxygen for a time ranging from 0.5 minutes to 30 minutes; then filtering said adsorbent from said oil and recovering said oil. The bleaching zone extends from the point that the temperature of the mixture is adjusted to within the above described range until bleaching equilibrium is closely approached or until a desired point on the way to bleaching equilibrium is reached.

With continuing reference to the succeeding stage or to each of the succeeding stages of this second embodiment, oil recovered from the preceding stage is admixed with fresh adsorbent to form a mixture. The formed mixture need not be deaerated or moisture adjusted since it is already in deaerated and moisture adjusted condition. The fresh adsorbent can be deaerated and moisture adjusted to a moisture content ranging from 0.05 to 0.25 percent by weight, if desired. If the adsorbent is added in the form of a concentrate with previously untreated oil, the concentrate can be deaerated or moisture adjusted if desired. However, not even the fresh adsorbent or concentrate is required to be deaerated or moisture adjusted since these are such a small part of the total system that their moisture and air content has essentially no efiect on the entire system, essentially all of which is already in deaerated and moisture adjusted condition. The oil/adsorbent mixture is temperature adjusted to a temperature in the range of 200 to 400 F provided the temperature is not already at a temperature in this range. Thus, no adjustment is necessary if oil recovered from a filtering step in a previous stage is already at a temperature in this required range. The oil/adsorbent mixture is then in each stage directly and continuously passed through a bleaching zone at atmospheric pressure or greater in the substantial absence of oxygen for a residence time of 0.5 minutes to 30 minutes. If a temperature adjusting step has been necessary in a particular stage, the bleaching zone in that stage extends from the point that the temperature of the mixture is adjusted to within the above described range until bleaching equilibrium is closely approached or until a desired point on the way to bleaching equilibrium is reached. If temperature adjustment in a particular stage has not been necessary, the bleaching zone extends from the first contact between adsorbent and oil in that stage during the admixing step until bleaching equilibrium is closely approached or until a desired point on the way to bleaching equilibrium is reached.

After the bleaching zone in each stage, the adsorbent is filtered from the oil, and the oil is recovered. Oil bleached to the desired degree is recovered from the final stage.

Thus, this second embodiment is a process for the adsorbent bleaching of refined edible oil utilizing reduced amounts of adsorbent. This process comprises from 2 to 7 stages with fresh adsorbent being utilized in each stage. The first stage comprises the steps of admixing oil with fresh adsorbent to form a mixture, deaerating said mixture and adjusting its moisture content to range from 0.5 to 0.25 percent by weight of the mixture, adjusting the temperature of said mixture to range from 200 to 400 F, directly and continuously passing said mixture through a bleaching zone at a pressure which is atmospheric pressure or greater in the substantial absence of oxygen for a time ranging from 0.5 minutes to 30 minutes, then filtering said adsorbent from said oil and recovering said oil. The succeeding stage or stages each comprise admixing oil recovered from the filtering operation in the previous stage with fresh adsorbent to form a mixture, adjusting the temperature of said mixture to range from 200 to 400 F provided the mixture is not already at a temperature within this range, directly and continuously passing said mixture through a bleaching zone at a pressure which is atmospheric pressure or greater in the substantial absence of oxygen for a time ranging from 0.5 minutes to 30 minutes, then filtering said adsorbent from said oil and recovering said oil. Oil bleached to the desired degree is recovered from the final stage.

Thus the process of this second embodiment is a multistage co-current process with incremental amounts of fresh adsorbent being utilized in each stage.

Preferably in this embodiment, in each stage the moisture level ranges from 0.075 to 0.15 percent by weight of the mixture, the temperature to which the mixture is adjusted ranges from 275 to 350 F, and the residence time in each bleaching zone ranges from 3 to 12 minutes.

In general, the more the number of stages utilized, the more efficient is the adsorbent usage, that is the less adsorbent totally is utilized.

It is preferred, however, to utilize two stages. This is because a two-stage process is economically the most practical considering both the equipment costs and the benefit achieved by more stages. In other words, most of the benefit of utilizing more than one stage is achieved by utilizing two stages. There is some benefit from an adsorbent usage standpoint of utilizing more than two stages but this is small. Because of the cost of equipment, a two-stage process is thus preferred.

This second embodiment reduces the amount of adsorbent utilized at least 20 percent compared to where a single stage process with conditions otherwise the same is utilized.

In a very preferred process for the bleaching of refined edible oils with adsorbent, the turbulent flow process of this invention is utilized in combination with the multistage incremental adsorbent addition process of this invention. In other words, preferably the second embodiment of this invention is utilized exclusively with turbulent flow in the bleaching zone in each stage. This process is referred to hereinafter as the combination process.

In other words, this combination process comprises from two to seven stages with fresh adsorbent being utilized in each stage. The first stage comprises the steps of admixing oil with fresh adsorbent to form a mixture, deaerating said mixture and adjusting its moisture content to range from 0.05 to 0.25 percent by weight of the mixture, adjusting the temperature of said mixture to range from 200 to 400 F, directly and con tinuously passing said mixture through a bleaching zone at a pressure which is atmospheric or greater and the substantial absence of oxygen under turbulent flow for a time ranging from 0.5 minutes to 30 minutes, then filtering said adsorbent from said oil and recovering said oil. The succeeding stage or stages each comprise admixing oil recovered from the filtering operation in the previous stage with fresh adsorbent to form a mixture, adjusting the temperature of said mixture to range from 200 to 400 F provided the mixture is not already at a temperature within this range, directly and continuously passing said mixture through a bleaching zone at a pressure which is atmospheric pressure or greater in the substantial absence of oxygen under turbulent flow for a time ranging from 0.5 minutes to 30 minutes, then filtering said adsorbent from said oil an recovering said oil. Oil bleached to the desired degree is recovered from the final stage.

Preferably, in this combination process, the amount of adsorbent utilized in each stage is equal to l00/n i 20% by weight of the total adsorbent to be utilized wherein n is the number of stages; two stages are utilized; the moisture level ranges from 0.075 to 0.15 percent by weight of the mixture; the temperature to which the mixture is adjusted ranges from 275 to 350 F; the residence time in each bleaching zone ranges from 3 to 12 minutes; each bleaching zone comprises a vertically oriented flooded packed column having a diameter ranging from 1.5 inches to feet, a height ranging from 5 feet to 30 feet, and a height to diameter ratio ranging from 3:1 to 75:1; the void space in a column ranges from 85 to 98 percent by volume; the packing is Pall rings; the flow .in a packed column has a Reynolds number ranging from 1 to 100, preferably 5 to 100.

In this combination process bleaching is accomplished to a required end point with an adsorbent savings of at least 50 percent compared to typical bleaching processes. For example, when soybean oil is bleached utilizing this combination process with two stages, total adsorbent usage (that is the total amount of adsorbent used in both stages together) ordinarily ranges from 0.15 to 0.25 percent adsorbent by weight of the oil. Usually, approximately half as much adsorbent can be utilized in this combination process as compared to the first embodiment of this invention.

Thus, in all the processes herein there is a substantial savings in adsorbent usage. This also results in a savings of oil.

The following Examples further illustrate the novel processes herein.

EXAMPLE 1 Single Stage Process Utilizing Turbulent Flow Ten pounds of Filtrol 105 adsorbent and 30 pounds of refined water washed soybean oil is fed into a stainless steel mixing tank having a diameter of 1.5 feet. These materials are admixed to form 40 pounds of adsorbent/oil mixture denoted a concentrate. The materials are blanketed with nitrogen during admixing.

The concentrate is then continuously admixed with 2,470 pounds of refined water washed soybean oil. This continuous admixing is carried out by continuously adding concentrate intoa pipe through which the main body of oil is continuously flowing. The concentrate is added into the pipe just previous to a pump. The concentrate is added into the flowing oil at a uniform rate all the time that oil is flowing through the pipe. The oil and adsorbent, that is the main body of the oil and the concentrate added to it, pass through the pump at a rate of 210 pounds/hour; this rate is maintained throughout the remainder of the process. Oil/adsorbent mixture emanating from the pump is formed almost instantaneously in the pump.

The refined water washed soybean oil which is utilized to form the concentrate and which makes up the main body of the oil has a moisture content of 0.5 percent by weight; it has a Lovibond Red color value of 10, and contains 0.5 ppm by weight chlorophyll. The adsorbent amounts to 0.4 percent by weight of the oil in the formed oil/adsorbent mixture. The oil/adsorbent mixture which is formed contains 2.5 percent oxygen by volume. The oil enters the previously referred to pump at a temperature of 120 F since this is the temperature at which the oil is received from the previous water washing operation.

The oil/adsorbent mixture emanating from the pump is continuously passed through a heat exchanger wherein its temperature is raised to 170 F.

The mixture is then continuously passed through a vacuum drier wherein it is deaerated so that it contains substantially no oxygen and has its moistured content reduced so that it contains 0.1 percent by weight moisture. The vacuum dryer is a stainless steel tank having a diameter of approximately 1.5 feet and a height of approximately 2 feet. Through the top of the tank is drawn a vacuum of approximately 26 inches of mercury, that is the absolute pressure in the tank is approximately 4 inches of mercury. The mixture is introduced into the top of the tank tangentially. It falls in the form of a thin film along the walls of the tank and is deaerated and moisture adjusted by the application of the vacuum. The mixture emits from the bottom of the tank in substantially deaerated form and having its moisture adjusted to 0.1 percent level mentioned above.

This deaerated moisture-adjusted mixture is then continuously fed through a heat exchanger where its temperature is adjusted to 310 F.

As a result of this temperature adjustment, the mixture enters a bleaching zone. This bleaching zone is made up of a portion of the previously mentioned heat exchanger, interconnecting piping and a'packed column. The mixture is directly and continuously passed through this bleaching zone.

In passing through the bleaching zone the mixture emitting from the heat exchanger is directly and continuously fed via interconnecting piping into the bottom of a vertically oriented packed column. The mixture is passed continuously through the column and emits from the top of the column.

0n startup the column is maintained in flooded condition by being filled with previously bleached oil. During processing, the column is maintained in flooded condition by being kept full of oil/adsorbent mixture at all times.

The column is 2.3 inches in diameter and has an effective height of 10 feet and an approximate height to diameter ratio of 52:1. It is packed with fiveeighths inch stainless steel Pall rings. 93 percent of the volume in the column is void space, that is, is not occupied by packing. The column is insulated so that the oil/adsorbent mixture passing therethrough retains the 310 F temperature to which it has been adjusted in the previous heat exchanger.

The mixture is passed through the bleaching zone under positive pressure in the substantial absence of oxygen and under turbulent flow. In particular, at the beginning of a run a pressure of approximately 5 psig is present in the bleaching zone as a result principally of back pressure from the filter which is down-stream from the packed column and is discussed hereinafter; this pressure graduallyincreases to 75 psig through the remainder of the run due to adsorbent buildup in the filter. This positive pressure and the flooded condition of the column assures the exclusion of oxygen. The mixture is passed through the column with flow providing a Reynolds number as previously defined of 5.

The residence time of the mixture in the bleaching zone is approximately 4.2 minutes with the residence time of the mixture in the packed column portion of the zone being 3.8 minutes.

The oil in the mixture emitting from the column is in fully bleached condition. It has a Lovibond Red value of 4 and contains less than 0.03 ppm by weight chlorophyll.

The mixture emitting from the top of the column is passed through a heat exchanger wherein its temperature is reduced to 260 F.

The mixture is then passed through a filter of the type described in Going et a1. U.S. Pat. No. 3,414,129, wherein the adsorbent and bleached oil are separated and the bleached oil is recovered out of the top of the filter. This filtering is carried out in the substantial absence of air. The recovered oil has a Lovibond Red value of 4 and a chlorophyll content of less than 0.03 ppm; it appears pale orange in color. Thus, complete bleaching is achieved in this Example with the use of only 0.4 percent adsorbent by weight of the oil processed which is a significant savings over the 1 percent which Bailey says is typical for bleaching soybean oil.

EXAMPLE 2 Two Stage Process With Non-turbulent Flow Refined water washed soybean oil having a moisture content of 0.5 percent by weight, a Lovibond Red color value of 10, a chlorophyll content of 0.5 ppm by weight, and an initial temperature of 120 F is bleached utilizing Filtrol as a bleaching adsorbent.

A concentrate is formed by admixing pounds of Filtrol 105 with 30 pounds of oil. Half of this concentrate is then continuously admixed with 2,470 pounds of oil in a first bleaching stage. This admixing is carried out by continuously injecting the concentrate into the oil just previous to a pump. These materials are-formed into oil/adsorbent mixture almost instantaneously in the pump. The mixture emits from the pump at a rate of 210 pounds per hour; this rate is maintained throughout the remainder of the process. The concentrate is added continuously so as to provide a concentration of adsorbent mounting to about 0.2 percent by weight.

The mixture emanating from the pump is continuously passed through a heat exchanger wherein its temperature is adjusted to 170 F. It is then continuously passed through a vacuum drier wherein it is deaerated and its moisture content is adjusted to 0.1 percent by weight.

This mixture is then continuously fed through a heat exchanger wherein its temperature is adjusted to 3 10 F.

As a result of this temperature adjustment, the mixture enters a bleaching zone. This bleaching zone is made up of a portion of the previously mentioned heat exchanger and of piping downstream of the heat exchanger. The mixture is directly and continuously passed through this bleaching zone.

The mixture is passed through the bleaching zone under positive pressure and in the substantial absence of oxygen. The flow through the bleaching zone is not turbulent. The residence time in the bleaching zone is approximately 4.5 minutes.

The mixture emitting from the bleaching zone has its temperature reduced to 260 F in a heat exchanger and is then passed through a filter of the type described in Going et al. U.S. Pat. No. 3,414,129 wherein the adsorbent and oil are separated and the oil is recovered.

This oil,which is still at 260 F, is then subjected to further bleaching in a second bleaching stage. In this second bleaching stage the oil from the first stage is first continuously admixed with the 20 pounds of remaining concentrate. Before admixing this concentrate is deaerated and moisture adjusted to contain 0.1 percent by weight moisture by passage through a vacuum drier. The concentrate is continuously admixed with the oil by continuously injecting the concentrate into the oil just previous to a pump. These materials are formed into oil/adsorbent mixture almost instantaneously in the pump. The concentrate is added previous to the pump so as to provide a concentration of adsorbent in the mixture amounting to about 0.2 percent by weight.

As a result of the contact between the oil and adsorbent, the mixture enters a bleaching zone. This bleaching zone is made up of the previously mentioned pump, piping downstream of the pump, a heat exchanger at the end of the piping, and piping downstream of the heat exchanger. In the heat exchanger the temperature of the mixture is adjusted to 3 10 F.

The mixture is passed through the bleaching zone under positive pressure and in the substantial absence of oxygen. The flow through the bleaching zone is mostly not turbulent. The residence time in the bleaching zone is approximately 4.5 minutes.

The mixture emitting from this bleaching zone has its temperature reduced to 260 F in a heat exchanger, and is passed through a filter of the type described in Going et a1. U.S. Pat. No. 3,414,129.

The oil recovered from filtration in this second bleaching stage has a Lovibond Red color value of 3.6 and a chlorophyll content of less than 0.015 ppm by weight. Thus complete bleaching is achieved in this Example with the use of only 0.4 percent adsorbent by weight which is a significant savings over the 1 percent which Bailey says is typical for bleaching soybean oil.

EXAMPLE 3 Two Stage Process with Turbulent Flow Refined water washed soybean oil having a moisture content of 0.5 percent by weight, a Lovibond Red color value of 10, a chlorophyll content of 0.5 ppm by weight, and an initial temperature of F is bleached utilizing Filtrol 105 as a bleaching adsorbent.

A concentrate is formed by admixing 5 pounds of Filtrol 105 with 15 pounds of oil. Half of this concentrate is then continuously admixed with 2485 pounds of oil in a first bleaching stage. The rest of the concentrate is deaerated and has its moisture adjusted to the 0.1 percent level in a vacuum drier and is reserved for a second bleaching stage.

The admixing of concentrate with oil in the first bleaching stage is carried out by continuously injecting the concentrate into the oil just previous to the pump. These materials are formed into oil/adsorbent mixture almost instantaneously in the pump. The mixture emits from the pump at a rate of 210 pounds per hour; this rate is maintained throughout the remainder of the process. The concentrate is added continuously so as to provide a concentration of adsorbent amounting to about 0.1 percent by weight.

The mixture emanating from the pump is continuously passed through a heat exchanger wherein its temperature is adjusted to F. It is then continuously passed through a vacuum drier wherein it is deaerated and its moisture content is adjusted to 0.1 percent by weight.

This mixture is then continuously fed through a heat exchanger wherein its temperature is adjusted to 310 F.

As a result of this temperature adjustment, the mixture enters a bleaching zone. This bleaching zone is made up of a portion of the previously mentioned heat exchanger, interconnecting piping and a packed column. The packed column is exactly as described in Example 1 and is operated as described in Example 1.

The mixture is directly and continuously passed through this bleaching zone. The mixture is passed through the bleaching zone under positive pressure in the substantial absence of oxygen and under turbulent flow. The pressure in the bleaching zone, the Reynolds number in the packed column and the residence time of the mixture in the bleaching zone and in the packed column is the same as in Example 1.

The mixture emitting from the bleaching zone has its temperature reduced to 260 F in a heat exchanger and is then passed through a filter of the type described in Goint et a1. U.S. Pat. No. 3,414,129. In this filter adsorbent and oil are separated and the oil is recovered.

The oil which is still at 260 F is then subjected to further bleaching in a second bleaching stage. In this second bleaching stage the oil from the first stage is first continuously admixed with the reserved deaerated moisture adjusted concentrate. The admixing is effected by continuously injecting the concentrate into the oil just previous to a pump. This addition is effected so as to provide a concentration of adsorbent in the resulting oil/adsorbent mixture of about 0.1 percent by weight.

As a result of the contact between the oil and adsorbent, the

mixture enters a bleaching zone. This bleaching zone is made up of the previously mentioned pump, piping downstream of the pump, a heat exchanger at the end of the piping, a packed column and piping connecting the heat exchanger and packed column. In the heat exchanger, the temperature of the mixture is adjusted to 310 F. The packed column is exactly as described in Example 1 and is operated as described in Example 1.

The mixture is directly and continuously passed through the bleaching zone under positive pressure (5-75 psig) and in the substantial absence of oxygen. The flow in the bleaching zone is turbulent (Reynolds number of the flow in the packed column is 5). The residence time in the bleaching zone is approximately 4.2 minutes with 3.8 minutes being the residence time in the column.

The mixture emitting from this bleaching zone has its temperature reduced to 260 F in a heat exchanger and is passed through a filter of the type described in Going et al. U. S. Pat. No. 3,414,129.

The oil recovered from filtration in this second bleaching stage has a Lovibond Red color value of 4 and a chlorophyll content of less than 0.03 ppm. Thus, complete bleaching is achieved in this Example with the use of only 0.2 percent adsorbent by weight which is a significant savings over the l percent which Bailey says is typical for bleaching soybean oil.

When in the above Examples other types of packing, for example, Raschig rings are substituted for the Pall rings utilized in the above Examples, equal bleaching results in terms of final Lovibond Red value and chlorophyll content are achieved with equal amounts of adsorbent utilization; however, due to adsorbent accumulation on the rings, pumping costs increase and the Raschig rings in the columns are desirably stream cleaned from time to time.

Other types of bleaching reactors other than the packed columns can be substituted for the packed columns in Examples l and 3 hereinbefore as long as these bleaching reactors provide turbulent flow. For example, a well stirred column containing baffies can be substituted for the packed column hereinbefore described with equal bleaching results.

' Other oils can be substituted for the refined water-washed soybean oil in Examples 1, 2, and 3 with the achievement of bleaching with significant savings in adsorbent over typical processes. For example, refined water-washed cottonseed oil having an initial Lovibond Red value of 4 and a chlorophyll content of 0.5 ppm can be bleached to a final Lovibond Red value of less than 2.5 and a final chlorophyll content of less than 0.03 ppm with adsorbent usage in Example 1 of 0.4 percent and in Example 2 of 0.4 percent and in Example 3 of 0.2 percent. Refined water-washed sunflower seed oil having an initial Lovibond Red value of 3 and a chlorophyll content of 0.3 ppm can be bleached to a final Lovibond Red value of less than 1 and a final chlorophyll content of less than 0.03 ppm with adsorbent usage in Example 1 of 0.2 percent, and in Example 2 of 0.2 percent an in Example 3 of 0.1 percent. Palm oil can also be substituted for soybean oil in the above Examples with the achievement of bleaching with significant savings of adsorbent, that is, with the use of 0.4 percent adsorbent by weight of the oil in Example 1, 0.4 percent of adsorbent by weight of the oil in Example 2, and 0.2 percent of adsorbent by weight of the oil in Example 3. Coconut oil can also be substituted for soybean oil in the above Examples with the achievement of bleaching with significant savings of adsorbent, that is, with the use of 0.2 percent adsorbent by' weight of oil in Example 1, 0.2 percent of absorbent by weight of oil in Example 2, and 0.1 percent of adsorbent byweight of oil in Example 3.

What is claimed is:

l. A process for adsorbent bleaching of refined edible oil utilizing 0.8% or less by weight of said adsorbent, said process comprising the steps of:

a. admixing said oil with said adsorbent to form a mixture;

1). deaerating said mixture and adjusting its moisture content to range from 0.05 to 0.25 percent by weight of the mixture;

c. adjusting the temperature of said mixture to range from 200 to 400 F;

d. directly and continuously passing said mixture through a bleaching zone at a pressure of atmospheric pressure or greater in the substantial absence of oxygen under turbulent fiow, the residence time of the mixture in said bleaching zone ranging from 0.5 to 30 minutes;

e. filtering said adsorbent from said oil and recovering said oil.

2. The process of claim 1 wherein in step (b) the mixture has its moisture content adjusted to range from 0.075 to 0.15 percent by weight of the mixture.

3. The process of claim 2 wherein in step (c) the temperature of said mixture is adjusted to range from 275 to 350 F.

4. The process of claim 3 wherein in step (d) the bleaching zone comprises a vertically oriented flooded packed column and the residence time in the bleaching zone ranges from 3 minutes to 12 minutes.

5. The process of claim 4 wherein said column has a diameter ranging from 1.5 inches to 10 feet, a height ranging from 5 feet to 30 feet, and a height-to-diameter ratio ranging from 3:1 to 75:1.

6. The process of claim 5 wherein the column is packed with Pall rings.

7. The process of claim 6 wherein the refined oil being bleached is refined soybean oil having a Lovibond Red value ranging from 9 to 15 and a chlorophyll content ranging from 0.2 to 1 ppm by weight, and said oil is bleached to a Lovibond Red value of less than 8 and a chlorophyll content of less than 0.1 ppm by the use of an adsorbent which is an acid-activated bleaching clay, said adsorbent amounting to 0.15 to 0.5 percent by weight of the oil.

8. The process of claim 7 wherein said adsorbent amounts to 0.35 to 0.45 percent by weight of the oil.

9. The process of claim 8 wherein filtration is carried out in the absence of oxygen.

10. A process for adsorbent bleaching of refined edible oil utilizing 0.8 percent or less by weight of adsorbent, said process comprising from 2 to 7 stages with fresh adsorbent being utilized in each stage, the first stage comprising the steps of a. admixing oil with adsorbent to form a mixture;

b. deaerating said mixture and adjusting its moisture content to range from 0.5 to 0.25 percent by weight of the mixture;

c. adjusting the temperature of said mixture to range from 200 F to 400 F;

(1. directly and continuously passing said mixture through a bleaching zone at a pressure which is atmospheric pressure or greater in the substantial absence of oxygen for a time ranging from 0.5 minutes to 30 minutes;

e. then filtering adsorbent from oil in the mixture and recovering said oil; the succeeding stage or stages each comprising the steps of a. admixing oil recovered from the filtering operation in a previous stage with fresh adsorbent to form a mixture;

b. adjusting the temperature of said mixture to range from 200 to 400 Fprovided the mixture is not already at a temperature in this range;

c. directly and continuously passing the mixture through a bleaching zone at a pressure which is atmospheric pressure or greater in the substantial absence of oxygen for a time ranging from 0.5 minutes to 30 minutes;

d. then filtering adsorbent from oil in said mixture and recovering the oil; oil bleached to the desired degree being recovered from the filtration operation in the final stage.

11. The process of claim 10 wherein the amount of adsorbent utilized in each stage is /n 20% by weight of the total adsorbent utilized wherein n is the number of stages.

12. The process of claim 11 wherein the moisture content in step (b) ranges from 0.075 to 0.15 percent by weight of the mixture, the temperature in steps (c) and (b ranges from 275 to 350 F and the time in steps (d) and (c ranges from 3 to 12 minutes.

13. The process of claim 12 wherein there are two stages.

,14. The process of claim 11 wherein in steps (d) and (c) the time is provided by directly and continuously passing the mixture through a bleaching zone under turbulent flow.

15. The process of claim 14 wherein each bleaching zone comprises a vertically oriented flooded packed column, the residence time in each bleaching zone ranging from 3 minutes to 12 minutes.

16. The process of claim 15 wherein in step (b) the moisture content ranges from 0.075 to 0.15 percent by weight of the mixture and in steps (c) and (b the temperature ranges from 275 to 350 F.

17. The process of claim 16 wherein each column has a diameter ranging from 1.5 inches to feet, a height ranging from 5 feet to 30 feet, and a height-to-diameter ratio ranging from 3:l to 75:1.

18. The process of claim 17 where the packing in said columns is Pall rings.

19. The process of claim 18 having 2 stages.

20. The process of claim 19 wherein in steps ((1) and (c) turbulent flow in the packed columns is defined by a Reynolds Number ranging from 1 to 100.

21. The process of claim 20 wherein the Reynolds number ranges from 5 to 100.

22. The process of claim 21 wherein the refined oil being bleached is refined soybean oil having a Lovibond Red value ranging from 9 to 15 and a chlorophyll content ranging from 0.2 to 1.0 ppm by weight and said less is bleached to a Lovibond Red value of less than 8 and a chlorophyll content of less than 0.1 ppm by weight by the use of an adsorbent which is an acid-activated bleaching clay, the total amount of said adsorbent utilized in both stages together amounting to 0.15 to 0.25 percent by weight of the oil. 

2. The process of claim 1 wherein in step (b) the mixture has its moisture content adjusted to range from 0.075 to 0.15 percent by weight of the mixture.
 3. The process of claim 2 wherein in step (c) the temperature of said mixture is adjusted to range from 275* to 350* F.
 4. The process of claim 3 wherein in step (d) the bleaching zone comprises a vertically oriented flooded packed column and the residence time in the bleaching zone ranges from 3 minutes to 12 minutes.
 5. The process of claim 4 wherein said column has a diameter ranging from 1.5 inches to 10 feet, a height ranging from 5 feet to 30 feet, and a height-to-diameter ratio ranging from 3:1 to 75:1.
 6. The process of claim 5 wherein the column is packed with Pall rings.
 7. The process of claim 6 wherein the refined oil being bleached is refined soybean oil having a Lovibond Red value ranging from 9 to 15 and a chlorophyll content ranging from 0.2 to 1 ppm by weight, and said oil is bleached to a Lovibond Red value of less than 8 and a chlorophyll content of less than 0.1 ppm by the use of an adsorbent which is an acid-activated bleaching clay, said adsorbent amounting to 0.15 to 0.5 percent by weight of the oil.
 8. The process of claim 7 wherein said adsorbent amounts to 0.35 to 0.45 percent by weight of the oil.
 9. The process of claim 8 wherein filtration is carried out in the absence of oxygen.
 10. A process for adsorbent bleaching of refined edible oil utilizing 0.8 percent or less by weight of adsorbent, said process comprising from 2 to 7 stages with fresh adsorbent being utilized in each stage, the first stage comprising the steps of a. admixing oil with adsorbent to form a mixture; b. deaerating said mixture and adjusting its moisture content to range from 0.5 to 0.25 percent by weight of the mixture; c. adjusting the temperature of said mixture to range from 200* F to 400* F; d. directly and continuously passing said mixture through a bleaching zone at a pressure which is atmospheric pressure or greater in the substantial absence of oxygen for a time ranging from 0.5 minutes to 30 miNutes; e. then filtering adsorbent from oil in the mixture and recovering said oil; the succeeding stage or stages each comprising the steps of a1. admixing oil recovered from the filtering operation in a previous stage with fresh adsorbent to form a mixture; b1. adjusting the temperature of said mixture to range from 200* to 400* F provided the mixture is not already at a temperature in this range; c1. directly and continuously passing the mixture through a bleaching zone at a pressure which is atmospheric pressure or greater in the substantial absence of oxygen for a time ranging from 0.5 minutes to 30 minutes; d1. then filtering adsorbent from oil in said mixture and recovering the oil; oil bleached to the desired degree being recovered from the filtration operation in the final stage.
 11. The process of claim 10 wherein the amount of adsor-bent utilized in each stage is 100/n + or - 20% by weight of the total adsorbent utilized wherein n is the number of stages.
 12. The process of claim 11 wherein the moisture content in step (b) ranges from 0.075 to 0.15 percent by weight of the mixture, the temperature in steps (c) and (b1) ranges from 275* to 350* F and the time in steps (d) and (c1) ranges from 3 to 12 minutes.
 13. The process of claim 12 wherein there are two stages.
 14. The process of claim 11 wherein in steps (d) and (c1) the time is provided by directly and continuously passing the mixture through a bleaching zone under turbulent flow.
 15. The process of claim 14 wherein each bleaching zone comprises a vertically oriented flooded packed column, the residence time in each bleaching zone ranging from 3 minutes to 12 minutes.
 16. The process of claim 15 wherein in step (b) the moisture content ranges from 0.075 to 0.15 percent by weight of the mixture and in steps (c) and (b1) the temperature ranges from 275* to 350* F.
 17. The process of claim 16 wherein each column has a diameter ranging from 1.5 inches to 10 feet, a height ranging from 5 feet to 30 feet, and a height-to-diameter ratio ranging from 3:1 to 75:1.
 18. The process of claim 17 where the packing in said columns is Pall rings.
 19. The process of claim 18 having 2 stages.
 20. The process of claim 19 wherein in steps (d) and (c1) turbulent flow in the packed columns is defined by a Reynolds Number ranging from 1 to
 100. 21. The process of claim 20 wherein the Reynolds number ranges from 5 to
 100. 22. The process of claim 21 wherein the refined oil being bleached is refined soybean oil having a Lovibond Red value ranging from 9 to 15 and a chlorophyll content ranging from 0.2 to 1.0 ppm by weight and said less is bleached to a Lovibond Red value of less than 8 and a chlorophyll content of less than 0.1 ppm by weight by the use of an adsorbent which is an acid-activated bleaching clay, the total amount of said adsorbent utilized in both stages together amounting to 0.15 to 0.25 percent by weight of the oil. 